SACS and Autosomal recessive spastic ataxia of Charlevoix-Saguenay: Mutations which lead to loss of function of the protein sacsin cause the neurodegenerative disorder Autosomal Recessive Spastic Ataxia of Charlevoix Saguenay or ARSACS (Engert et al., 2000; Fogel and Perlman, 2007; Martin et al., 2007).